Universal bases for thermionic valve tubes



0a. 25, 1960 r c. Km

UNIVERSAL BASES FOR THERMIONIC VALVE Filed June 5, 1956 2 Sheets-Sheet 1 INVEN TOR.

CHESTER KIRKA Oct. 25, 1960 v KlRKA 2,958,006

UNIVERSAL BASES FOR THERMIONIC VALVE TUBES Filed June 5, 195s v 2 Sheets-Sheet 2 my aim lww mum IN VEN TOR.

CHESTER KIRKA United States Patent UNIVERSAL BASES FOR THERMIONIC VALVE TUBES Chester Kirka, Stratford, C0nn., assignor, by mesne assignments, to The Machlett Laboratories, Incorporated, Springdale, Conn, a corporation of Connecticut Filed June 5, 1956, Ser. No. 589,469

Claims. (Cl. 315-58) This invention relates to thermionic valves and has particular reference to thermionic valves having novel bases which are adaptable for universal mounting in any of several types of supporting structures.

Thermionic valves of the type referred to herein are generally high-voltage half-wave rectifier tubes, with thoriated tungsten filaments, which tubes are used in X-ray apparatus, generally in the power supply circuit for an X-ray tube. Such tubes are intended for oilimmersed operation and have, in the past, been made with any one of several types of bases for mounting in a particular type of existing socket.

Many X-ray equipment manufacturers require valve tubes having bases constructed to fit into their own particular equipment but having similar electrical characteristics. Also, field service organizations are required to provide several types of equipment with tubes having similar electrical characteristics. It is, therefore, desirable for a tube manufacturer to supply all equipment manufacturers and service organizations with a universal tube if possible. However, in the past this could not be done because the various equipment manufacturers were not standardized on their types of sockets for receiving the tubes.

In still other instances it has been necessary to pro vide valve tubes for use in equipment which supplies to the tubes filament voltage which is higher than the voltshowing two different methods of adapting the invention for use in plug-in or snap-in sockets;

age at which the filaments are designed to operate most satisfactorily.

Accordingly, it is a primary object of the present invention to provide an electron discharge device having a base of novel construction adaptable for mounting in various types of sockets.

Another object is to provide electron discharge devices having improved means for easily and simply adapting the devices for use in circuits providing either low or relatively high voltages to the filaments thereof.

Another object is the provision of a thermionic valve tube having a base so constructed and arranged that it may be mounted in various plug-in, screw-in or snap-in types of sockets, and may be used with or without a removable resistance wire in series with the filament of the tube, whereby the filament voltage may be controlled.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings, in which:

Fig. 1 is an elevational view partly in section of a tube embodying the invention;

Fig. 2 is a plan view of the base of the tube shown in Fig. 1;

Fig. 3 is an enlarged fragmentary sectional view taken substantially on line 3-3 of Fig. 2 looking in the direction of the arrows;

Fig. 4 is a fragmentary elevational View of a portion of the base shown in Fig. 2;

Figs. 5 and 6 are elevational views partly in section Fig. 7 is a view similar to Fig. 5 showing the addition of means for reducing filament voltage; and

Fig. 8 is a fragmentary sectional view showing a base adapted for mounting in a screw-in type of socket.

Referring more particularly to Fig. 1, the valve tube illustrating the preferred embodiment of the invention comprises a glass envelope having a cylindrical central portion 9 and end portions 10 and 11 of reduced diameter. Within end portion 10 are supports 12 for a tubular anode 13 which extends longitudinally within the enlarged central portion 9. Enclosing the anode end of the envelope is a dielectric cap 14 the base of which carries an anode terminal 15. The cap 14 is rigidly afiixed to the envelope and the terminal 15 is interchangeably mounted as by threading into the cap, thus providing rugged means whereby the tube may, if desired, be supported in position of use, and supplying anode potential through lead 12a to anode 13.

The opposite end portion 11 of the envelope has a reentrant portion 16 which terminates in a stern press 17. Two spaced filament supports 18 and 19 extend through the stem press 17 and to each support is fixed one end of a catenary type filament 20, the central portion of the filament being supported by one end of a third support 21 which has its opposed end fixedly mounted in the stem press 17.

A shield 22 is mounted over the stem press 17 and adjacent portions of the filament supports to protect them from electron bombardment.

The outer ends of filament supports 18 and 19 terminate slightly outwardly from the stem press 17 within the recess formed by the reentrant portion 16, and to the end of each support 18 and 19 is fixed one end of a respective flexible lead 23 and 24.

Mounted over the cathode end of the envelope is a base 25 having a tubular flange portion 26 which encloses and is rigidly secured to envelope portion 11 by a suitable cementitious material 27. Base 25 is preferably formed of molded dielectric material such as Bakelite or other hard plastic material, and during the molding process three small metal plates are embedded in the base flush with its outer surface. The metal plates, indicated respectively by numerals 28, 29 and 3% in Fig. 2, are flat and relatively thin, and provide the dielectric base 23 with three separate spaced electrically conductive portions. 7

The outer end of flexible filament lead 2-3 extends into the base 25 and is secured directly to plate 29. The other lead 24 is similarly connected directly with plate 30 (see Fig. 3). Thus the plates 29 and 30 become part of the filament circuit.

Plate 29 is provided with a threaded opening 31 therein, plate 28 has three threaded openings 32, 32a and 32b, and plate 30 has three threaded openings 33, 33a and 33b. All of the threaded openings are located at predetermined positions in the plates and are adapted to be selectively used in connecting the tube into various types of equipment. Metal terminals of selected lengths are adapted to be inserted into selected openings and to thus provide means for supplying power to the filament, as will be described. To insure satisfactory electrical contact between the metal plates and the metal terminals, each of the openings mentioned above are actually provided with metal bushings of a length suflicient to extend through the base 25 and plates. This is illustrated in Fig. 3 wherein a bushing 34 is provided in opening 33b, a bushing 35 is provided in opening 33, and a bushing 36 is provided in opening 32a.

Over the end of the base 25 is positioned a removable cap 37 which rests upon the base so as to provide a chamber therebetween. The cap 37 covers plates 28, 29 and 30 and prevents accidental shorts, and also protects the glass tubulation 38 (Fig; l) of the envelope from being damaged. The cap 37 is held in place by the terminals which connect the tube to a source of electrical energy.

Assuming that the equipment into which valve tubes of the presently described type are to be inserted is arranged to supply relatively low filament voltages to tubes having metal terminals of predetermined selected lengths and spaced relation, such tubes can be made to fit the equipment by first electrically connecting plate 28 with plate 29 by a metal jumper or connector 39 (Fig. 4) which is held in place at each end by screws 40 inserted in openings 31 and 32. Thus, plate 28 becomes part of the filament circuit.

If the equipment is designed to supply relatively low filament voltage to tubes with metal terminals which are approximately three-eighths inch long, for example, spaced on centers about one inch apart, the structure will appear substantially as shown in Fig. 5. The terminals 41 and 42 are each provided with respective screws or bolts 41a which extend through openings in the cap 37 and are threaded into selected openings 32b and 33a in plates 28 and 30 respectively. Thus a circuit is completed through terminal 41, plate 28, jumper 39 and plate 29 to one side of the filament 20 and through terminal 42 and plate 30 to the other side of the filament.

If the equipment is designed to supply relatively low filament voltage to tubes having metal terminals approximately one inch long, for example, spaced on centers about one and one-quarter inches apart, the structure will appear substantially as shown in Fig. 6. Terminals 43 and 44 are mounted on bolts 43a which extend through openings in the cap 37 and are threaded into selected openings 32a and 33b in plates 28 and 30 respectively. Thus a circuit is completed from terminals 43 and 44 through filament 20 as in the construction of Fig. 5.

Assuming that the equipment into which tubes are to be inserted is arranged to supply relatively high filament voltages to tubes having terminals as shown in Figs. and 6, the tubes can be easily accommodated in the equipment by placing a resistor in series with the filament for reducing the efiective filament voltage to a level at which the filament is designed to operate. For example, a filament which is designed to operate at six volts can be used in equipment which supplies higher voltage, such as ten volts, to the terminals.

This is done, in accordance with the present invention, by removing the jumper 39 and substituting in its place a high resistance wire 45 (Fig. 7). The wire 45 is preferably in the form of a coil which is placed around the circumference of the tubular portion 26 of base 25 adjacent cap 37, the end portions of the wire being held in fixed relation by an insulator 46. The ends of the wire pass from the insulator 46 through a recess 47 into the interior of the cap 37 and are connected to the respective plates 28 and 29 by the screws 40. The resistor wire 45 thus replaces the jumper 39. Otherwise, the circuitry from the terminal through the filament is the same as described in connection with the structures of Figs. 5 and 6.

Figs. 1 and 8 illustrate a tube base structure which may be mounted in screw-in types of sockets. The base carries a plug 48, one terminal 49 of which is centrally located and connected by bolt 50 to plate 30, bolt 50 extending through plug 48 and being inserted through an opening in the cap 37 and into opening 33 in plate 30. The other terminal 51 engages a metal pin 52 carried by the plug 48, pin 52 extending through an opening in cap 37 and projecting into an unthreaded opening 53 in plate 28. Pin 52 is split at its end as shown at 54 and 4 thus is adapted to be forced tightly into the opening and into good electrical contact with plate 28.

This type of terminal means can be used with either the jumper 39 or resistor wire 45, depending on the voltage supplied to the filament by the particular equipment in which the tube is to be used.

It is to be understood that the terminals can also take other forms such as the forms shown and described in US. Patent No. 2,890,385.

From the foregoing description it is apparent that an improved base structure for thermionic valve tubes has been provided in accordance with the objects and advantages of this invention.

It is also apparent that various changes and modifications may be made by those skilled in the art without departing from the scope of this invention. Therefore, all matter shown and described is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A thermionic valve tube comprising an envelope containing an electrode, a dielectric base mounted on one end of the envelope, a plurality of electrically conductive members mounted on the base and insulated from each other and having a plurality of openings at predetermined locations therein, two of the conductive members being first and second fixed contacts, means connecting the fixed contacts to respective ends of the electrode, a removable dielectric cap mounted over the base and conductive members, the cap having a plurality of openings therethrough adapted to be aligned with the openings in the conductive members, a first interchangeable terminal removably located on the cap and having a portion ex tending through a selected opening therein into an aligned opening in the first fixed contact, and a second interchangeable terminal removably located on the cap and having a portion extending through a second selected opening therein into an aligned opening in a conductive member other than the first fixed contact.

2. A thermionic valve tube substantially as set forth in claim 1 wherein the conductive member into which the second terminal extends is a contact additional to said first and second fixed contacts, and a strip of conductive material is connected at one end to the second fixed contact and at its opposed end to the member in which the second terminal is extended.

3. A thermionic valve tube substantially as set forth in claim 1 wherein the conductive member into which the second terminal extends is a contact additional to said first and second fixed contacts, and a length of high resistance wire is wound around the circumference of the base with its ends penetrating into the interior of the cap, one end being connected to the second fixed contact and the opposed end being connected to the member in which the second terminal is extended.

4. A base for an electron discharge device having an envelope with an electrode therein and leads for the electrode extending through the envelope, said base comprising a disc of dielectric material having a plurality of electrically conductive members embedded in the material of the disc and spaced from one another, two of the members being first and second contacts which are respectively electrically connected to the leads for the electrode, a removable dielectric cap mounted over the base in spaced relation thereto and to the conductive members, the cap and conductive members having a plurality of aligned openings therein, a pair of removable terminals mounted on the outer side of the cap, and means electrically connecting the terminals to respective selected conductive members and simultaneously holding the terminals on the cap and the cap on the base, which means comprises connecting means extending from the terminals, through openings in the cap, and through the space between the cap and base, and into disengageable securement within the aligned openings in the base.

5. A valve tube as set forth in claim 1 wherein the 2,958,006 5 electrically conductive members are two in number, References Cited in the file of this patent wherein the removable dielectric cap has two openings therethrough which are adapted to be aligned with two UNITED STATES PATENTS of the openings in the electrically conductive members, 730,768 Hoelscher June 9, 1903 and wherein the first and second terminals extend re- 5 1,075,365 McNeel Oct. 14, 1913 spectively into said two of the openings in the electrically 1,585,878 Rugh May 25, 1926 conductive members. 1,595,535 Wood Aug. 10, 1926 2,030,254 Hensel et a1. Feb. 11, 1936 2,216,247 Ledig et'al. Oct. 1, 1940 10 2,743,393 Atlee et a1. Apr. 24, 1956 

